Experimental Investigation of CCN and IN Abilities of Various Aerosol Types in the MRI Cloud Simulation Chamber

A variety of aerosol species has an inherent ability to act as CCN and/or IN, and some of them actually activate under conditions relevant to the atmosphere. An accurate and quantitative description of the relation between physicochemical and biological properties of aerosol particles and their activity and potential role in cloud formation is a crucial subject for improvement of numerical cloud simulation and weather/climate prediction models. To overcome the current lack of understanding of aerosol-cloud-precipitation interactions and to reduce the uncertainty in estimates of the aerosol indirect effects, we are attempting to propose novel incorporate parameterizations that link aerosol particles and cloud particles from the experimental approaches. A cloud simulation chamber facility run by the Meteorological Research Institute (MRI) has been used to investigate the details of the fundamental processes of cloud formation. The MRI cloud chamber was designed as an adiabatic-expansion-type cloud chamber covering temperatures from 30 to-100°C, pressures from 1030 to 30 hPa, and an evacuation rates corresponding to ascent rates from 0 to 30 m s-1. Results from the preliminary experiments demonstrated the accuracy of coordinated pressure and temperature controls to reproduce cloud formation processes (both dry and wet adiabatic expansion processes) and the ability of the chamberʼs instrumentation to measure aerosol, cloud droplet, and ice crystal characteristics (Tajiri et al. 2013). Performance tests demonstrate the chamberʼs usefulness as a facility to investigate cloud droplet and ice crystal formation processes through the activation of various types of aerosol particles. In addition to the well-known aerosol types such as ammonium sulfate, dust and soot, we are currently capable of handling variety of specific aerosol particles and certified reference materials including the biological aerosols (Snomax, Bacillus Subtilis and Pollen), the artificial ice nuclei (AgI), etc. This paper focuses on the MRI dynamic cloud chamber experiments in progress and shows results from the experiments of various types of specific aerosol particles.